The invention relates to a process for shifting sour gas portions within a natural gas network. The process can be used for natural gas types that contain not only useful substances, such as methane, higher hydrocarbons, hydrogen and carbon monoxide impurities, such as hydrogen sulphide, organic sulphur components, e.g. mercaptanes, and carbon oxysulphide, but also carbon dioxide and water vapour in different portions.
As a rule, the sulphur components contained in the raw natural gas have to be removed to obtain a residual content of only a few ppm to permit further industrial utilization of the natural gas. The removal of hydrogen sulphide, mercaptanes, carbon dioxide and other sour gas constituents from industrial gases is generally performed with the aid of chemically acting absorbents, such as amino solutions, alkali salt solutions, etc. or physically acting, chemically non-active absorbents, such as Selexol, propylene carbonate, N-methyl pyrrolidone, Morphysorb, methanol, etc. in loop systems, the physically acting absorbents (as opposed to chemical scrubbing agents) being capable of removing organic sulphur components. In this process, the carbon dioxide contained in the gas is removed partially, totally or only in a portion as little as possible, depending on the requirements and specifications.
Normally, the sour gas from the absorbent regeneration unit is further processed to sulphur in a Claus plant. In this connection, the separation capacity of the sour gas absorption unit and the related processing capacity of the Claus plant impose restrictions on the quantity of sour gas that can be absorbed from the natural gas and this consequently also applies to the throughput of natural gas that can be purified by absorption.
Plants of this type exist in large numbers and at various locations. It is often a problem that the sour gas content varies during the exploitation of natural gas resources, in particular that the said content increases. Any increase in the sour gas content of the natural gas at the same rate of exploitation would thus lead to an overload of the sour gas separation unit and of the Claus plant as well. Hence, the natural gas production rate would have to be decreased or the existing plants would have to be retrofitted with the necessary, expensive equipment, so that the respective other plant simultaneously would have free capacities in the event of smaller sour gas portions or lower production rates.
There has been a keen interest for a long time already in finding an efficient facility for the shifting of sour gas contained in natural gas from the overloaded sour gas separation units and related Claus plant to such separation units with Claus plant that have free capacities in order to operate all units involved at their maximum natural gas capacity.
The aim of the invention, therefore, is to provide a process that permits a simple and efficient shifting of sour gas portions in the natural gas to such sour gas separation units with Claus plant that have free/free capacities.